Cartridge for pickup

ABSTRACT

An electromagnetic pickup cartridge comprises a needle support mounted for vibration in accordance with sound tracks on a record engaged by a needle mounted on the support, and includes two pairs of pole pieces mounted in spaced parallel relation, with each pair including a first pole piece and a second pole piece interconnected by a respective magnetic coil holder. The two first pole pieces have pole faces at corresponding ends thereof in spaced relation with the support, and with the pole faces extending in perpendicular facing relation to each other. Respective coils embrace each pole piece, with the coil on each second pole piece being wound reversely relative to the coil on the associated first pole piece and connected in series therewith. Thereby, external magnetic fluxes are cancelled, with respect to each pair of pole pieces, so that high fidelity reproduction is provided in all channels of the record by the first pole pieces and the coils thereon in accordance with vibrations of the support relative to the pole faces. The support may comprise a paramagnetic metal tube in operative association with a fixedly position permanent magnet, or may comprise a tubular permanent magnet. Tension means are provided to preset the fulcrum of the support, and a mu-metal member is paced near the pole faces and the support to form a vertical compensation plate. From the physical standpoint, the pickup cartridge comprises a cartridge case mounting the pole pieces and a needle case mounting the needle support and readily assembled with the cartridge case.

United States Patent Ikeda 51 3,665,123 [451 May 23, 1972 [54] CARTRIDGE FOR PICKUP Kazuhiro lkeda, Numazu, Japan Messrs. Kabushiki Kaisha Mitachi Onkyo Seisakusho, Ohoka, Numazu-shi, Japan [22] Filed: May 22,1970

[21] Appl.No.: 39,613

[72] Inventor:

[73] Assignee:

3,526,728 /1970 lga ....l79/100.4l K 3,146,319 8/1964 Stanton.... ....l79/100.41K 3,463,889 8/1969 Ahrens ....l79/l00.41 K 3,118,978 1/1964 Pritchard et ..l79/l00.4l K

Primary ExaminerRobert L. Griffin Assistant ExaminerRichard K. Eckert, Jr. AtwrneyMcGlew and Toren [57] ABSTRACT An electromagnetic pickup cartridge comprises a needle support mounted for vibration in accordance with sound tracks on a record engaged by a needle mounted on the support, and includes two pairs of pole pieces mounted in spaced parallel relation, with each pair including a first pole piece and a second pole piece interconnected by a respective magnetic coil holder. The two first pole pieces have pole faces at corresponding ends thereof in spaced relation with the support, and with the pole faces extending in perpendicular facing relation to each other. Respective coils embrace each pole piece, with the coil on each second pole piece being wound reversely relative to the coil on the associated first pole piece and connected in series therewith. Thereby, external magnetic fluxes are cancelled, with respect to each pair of pole pieces, so that high fidelity reproduction is provided in all channels of the record by the first pole pieces and the coils thereon in accordance with vibrations of the support relative to the pole faces. The support may comprise a paramagnetic metal tube in operative association with a fixedly position permanent magnet, or may comprise a tubular permanent magnet. Tension means are provided to preset the fulcrum of the support, and a mu-metal member is paced near the pole faces and the support to form a vertical compensation plate. From the physical standpoint, the pickup cartridge comprises a cartridge case mounting the pole pieces and a needle case mounting the needle support and readily assembled with the cartridge case.

8 Clains, 16 Drawing Figures Patented May 23, 1972 4 Sheets-Sheet l 2 WTWA W H AH D M mil TO R E w W2 A K Patented May 23, 1972 3,665,123

4 Sheets-Sheet INVENTOR KAZUHIRO IKEDA BY mkyaw 1 Tm Patented May 23, 1972 4 Sheets-Sheet Z INVENTOR KAZUHIRO IKEDA my) 9 E101 Patented May 23, 1972 3,665,123

4 Sheets-Sheet 4 FIG. l3 FIG. ll

FIG. I4 5 Y INVENTQR NAZUHIRO IKEDA mcwikm SUMMARY OF INVENTION The present invention generally relates to an electro-mag netic pickup and further to a pickup cartridge for a stereo record in which sound grooves provided on the opposite walls of one groove, and a stereo record in which the directions of modulation of two sound grooves are perpendicular to each other as is at present quite general.

Many magnetic pickups are designed for reproduction of these records but there remain problems, great or small, in all these pickups. The object of the present invention is to solve these problems and to provide a pickup cartridge in which the problems are kept at the minimum.

According to a feature of the present invention which will be stated later, it is possible to shift a resonance point outside the audio-frequency by reducing the vibration mass of a needle assembly, and a decrease in this mass greatly reduces distortion and thus there is obtained an effect that the distortion is absorbed in the sound grooves of record during reproduction.

In accordance with another feature of the present invention, during needle assembling, it is possible to do without inserting the needle in a holder by bringing a needle fulcrum close to the surface of the record in order to obtain an optimum tracking angle. Arranging a vibrator outside a pole piece facilitates assembling and inspecting. Furthermore, by the use of a vertical compensation plate, it becomes possible to simply keep a channel vibration at 25db or more.

The object of only taking out an output voltage is sufficiently achieved by means of only a coil near the vibrator, but the present invention is characterized in that four coils are used and the mutual coils of each channel are differentially wound and provided so as to cancel external magnetic induction. The coil especially provided serves for the increase in output voltage and the present invention is widely different from the conventional variable reluctance type in respect of this point. In the conventional electro-magnetic type in which four coils are employed, the coils of each channel are cross connected by means of the yoke in view of the generator type and this causes crosstalk unless sufiicient precautions are taken. In the present invention, however, there is no necessity to cross each coil, so that the present invention serves to decrease crosstalk. It is needless to say that crossing of the yoke practically does not cause any problem.

BRIEF DESCRIPTION OF THE DRAWINGS In the Drawings FIG. 1 is a perspective view of a first embodiment of the invention for the explanation of the principle of the present invention;

FIG. 2 is a vertical section view;

FIG. 3 is a plan view ofa needle case;

FIG. 4 is a front view thereof;

FIG. 5 is a rear view thereof;

FIG. 6 is a plan view ofa cartridge case;

FIG. 7 is a front view of FIG. 6;

FIG. 8 is a side view ofthe cartridge case;

FIG. 9 is a perspective view of a second embodiment for the explanation of the principle of the present invention;

FIG. 10 is a vertical section view thereof;

FIG. 11 is a plan view ofa needle case;

FIG. 12 is a front view thereof;

FIG. 13 is a rear view thereof;

FIG. 14 is a plan view ofa cartridge case;

FIG. 15 is a front view of FIG. 14; and

FIG. 16 is a side view ofthe cartridge case.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pickup shown in FIGS. 1-8 has a cartridge case 18 com other end. An electro-rnagnetic circuit is contained in the case 18 and in a stereo type the circuits end at contact pins 26, 27 and each circuit has a pair of coil forms 22 and a respective coil form holder 5 or 6 and is equipped with a respective polepiece 1 or 3, with the two pole pieces being in position opposite to each other. As seen in FIG. 1, the pole pieces 1, 3 face each other at an angle of Each coil form holder 5 and 6 has a pair of spaced legs extending therefrom in substantially parallel relation. The legs of coil form holder 5 are juxtaposed with respective pole pieces 1 and 2, and those of coil form holder 6 are juxtaposed with respective pole pieces 3 and 4. Pole pieces 1 and 2 are wound with respective windings 8 and 7, which are wound in respective opposite directions and connected in series with each other. Pole pieces 3 and 4 are wound with respective windings 10 and 9, which are wound in respective opposite directions and are connected in series with each other.

The two magnetic circuits are enclosed in cases 20, 21 of p. materials, and the cases 20, 21 of a materials are secured to the inside of the cartridge case 18 with a part partially projected to the outside. Each coil is connected to a respective contact pin 19 by means of a respective lead wire 28 with soldering or the like. A cover 29 is fixed to the hollow pan of the case 18 with adhesive. As shown in FIGS. 2 to 5, in the needle case 23 there are grooves 30 adapted to projections 31 of the cartridge case 18 in order to carry out the needle assembling at a proper angle. A needle support is provided to hold the needle, and includes a very light but strong aluminum tube 13, for example, which is mounted in a short tube 12 forming a vibrator of magnetic material, such as soft iron, and which is supported by a suitable elastic body 15 which may be rubber.

A permanent magnet 11 is fixedly positioned in cartridge case 18 under tube 12 (hereinafter referred to as the vibrator) in such a manner that permanent magnet 11 may come just under the pipe 12, forming the vibrator, when the needle case 23 is fitted to the cartridge case 18, whereby the vibrator 12 is magnetized. By this arrangement, the needle 14 can freely move in a desired plane, namely at a proper angle to the direction of the record groove. It will be noted that tube 12 overlies the pole pieces 1 and 3, and terminates at the inner edges of these pole pieces. Grooves 32 of the needle case 23 position damper rubber 15 and the damper rubber 15 is accurately fixed by a damper adapter 24. Grooves 33 of needle case 23 form openings for pole pieces 1, 3, and grooves 34 of needle case 23 receives fixing a metal plate 17, which controls the movement of the vibrator 12, and fixes a tension wire 16 for determining the fulcrum of vibration.

The needle case 23 is moved in the direction indicated by arrow F in FIG. 2 until it just fits on the projections 31 of cartridge case 18. Grooves 35 (FIG. 6 and FIG. 8) serves to position the cartridge accurately a pickup arm.

The function of this embodiment of the present invention will be explained below, mainly with reference to FIG. 1.

A movement transmitted to the needle 14 by a record is transmitted to the vibrator 12 through the cantilever 13, and vibrator 12, arranged very close to the surfaces of pole pieces 1, 3, causes a magnetic flux variation in these pole pieces responsive to modulations in the wall or walls of the record groove.

When a record of 45 45 is played and a needle point traces the groove on the inner side, the vibrator 12 approaches the surface of the pole piece 3 or separates therefrom, and an output voltage responsive to a modulation is obtained in a coil wound on pole piece 3. At this time, vibrator 12 moves perpendicularly to the surface of pole piece 3, as mentioned, so that vibrator 12 moves parallel to the surface of pole piece 1 at a constant distance therefrom. Consequently, no variation in magnetic flux is generated in pole piece 1, but a variation in magnetic flux is generated in pole piece 3. When the needle point traces the outside of the groove, the function is, needless to say, conducted quite reversely to the above statement. Although the effects of the structure and its function vary, a permanent magnet may be used instead of the vibrator 12 and a fixed magnet 11.

Since the vibrator 12 of the present device is not in the pole piece structure, as in the stainless magnetic cartridge, the fulcrum of the needle case 23 is further approachable to the surface of the record and can reach an optimum vertical tracking angle (15), and the vertical movement of the needle closely follows the direction to which a vertical modulation is cut in the record. A very severe vertical tracking distortion is thereby substantially eliminated.

Among the advantages of the present invention are that the needle case 23 eliminates the difficulties hitherto necessary to insert a needle assembly into a long holder, and simplifies the assembly of two parts. Additionally, assembly and inspection are facilitated because all parts of the movable needle structure appear on the outside of the cartridge. By using a cantilever arm, of non-ferrous metal and very light weight, to support the needle, the effective mass at the needle-point is remarkably decreased as compared to a general moving magnet. The decrease in the mass obtained thereby changes the vibration mass of the cantilever of the movable needle, so that a resonance occurs at a frequency higher than the audiofrequency zone, whereby distortion of the sound is obviated. The decrease in this mass extends the life of the record.

A cartridge of the second embodiment as shown in FIGS. 9-16, has a cartridge case 18 comprising a suitable plastic material, a terminal plate 25 with contact pins 19 mounted at one end of the case 18, and a needle case 23, detachable from the case 18, connected to the other end. An electro-magnetic circuit is contained in case 23. In a stereo type pickup, the circuits end at respective contact pins 26 and 27, and each circuit includes a pair of windings on coil forms 22 on coil hol ders 5, 6, and further includes two pole pieces 1, 3 arranged opposite each other in facing relation. As best seen in FIG. 9, these pole pieces or faces are in perpendicular facing relation with each other.

Two sets of these magnetic circuits are positioned in cases 21, 22 of p. materials and the cases 20, 21 are secured to the inside of the cartridge case 18 with a part of these cases partially projected to the outside. Each coil is connected to a respective contact pin 19 by means of a respective lead wire 28, and is securely fitted to with soldering or the like. A cover 29 is fixed to the hollow part of the case 18 with adhesive. As shown in FIGS. 10 to 13, in the needle case 23 there are grooves 30 adapted to a projections 31 of the cartridge case 18 in order to carry out the needle assembling at a proper angle. A cantilever support for the needle includes a light but strong aluminum tube 13 inserted into a tubular vibrator 12 comprising magnetic materials such as soft iron supported by a suitable elastic body ofa material like rubber.

Grooves 32 of the needle case 23 position damper rubber l5, and the damper rubber 15 is accurately fixed by a damper adapter 24. Grooves 33 of case 23 provide openings for the pole pieces 1, 3.

The needle case 23 is moved in the direction indicated by arrow F in FIG. 10 until it just fits on the projection 31 of the cartridge case 18. Grooves 35 (FIG. 14 and FIG. 16) serve to seat the cartridge on a pickup arm. It will be observed that vibrator 12 overlies, in spaced relation, pole pieces 1 and 3 and terminates at the inner edges of these pole pieces.

The function of this embodiment will be explained below, with reference to FIG. 9.

A movement transmitted to the needle 14 by a record is transmitted to the vibrator 12, comprising a permanent magnet, through the cantilever 13, and the vibrator 12 arranged extremely close to the surfaces of a pair of pole pieces 1, 3, and causes a magnetic flux variation in the pole piece in response to a modulation in the record groove wall.

At this time, in order to improve a channel separation, it is necessary to equalize the output voltage in the lateral direction to that in the vertical direction.

In FIG. 9, numeral 36 indicates a vertical compensation plate which is made of pi material such as permalloy or the like and, by placing this plate, a channel separation can simply be kept at db or more. The largest dispersion in the conventional stereo cartridge was a channel separation but vertical compensation plate 36 eliminates this defect. The function of plate 36 will be explained below. The movement transmitted to a record needle 14 is transmitted to the vibrator 12 through the cantilever 13. At this time, considering the lateral direction and the vertical direction, in the lateral direction, when the vibrator 12 is between the pole pieces 1 and 3 at first, magnetic fluxes of the same quantity flow in the pole pieces 1 and 3 respectively but when this balance is lost, for instance, when the vibrator 12 approaches the pole piece 1, the magnetic flux of the pole piece 1 is increased and the magnetic flux of the pole piece 3 is decreased. When this magnetic flux is increased or decreased by the same quantity, the L and R channels can obtain the same output respectively. In this case, since these channels are entirely disymmetrical, they are well balanced. Next, considering the vertical direction, in FIG. 9, the vibrator 12 vertically vibrates but, namely, in case the vibrator 12 moves in the direction of y-y' and in case it moves in the direction of x-x', the direction of x-x' is entirely symmetrical but the direction of y-y is not symmetrical, so that the quantity of magnetic flux variation varies depending upon the above two different directions. In the case of the direction of y-y', a quantity of magnetic flux variation is smaller than the case of the direction of x-x' and consequently the output is not entirely the same. In order to compensate this difference, the vertical compensation plate 36 is provided, whereby it is possible to equalize the output voltages, namely, the quantity of magnetic flux variation in the .r-x' direction to that in the y-y direction, and channel separation can be improved.

In FIG. 9, the whole function will be explained below. When a record of 45-45 type is played and a needle-point traces the groove on the inner side, the vibrator l2 approaches the surface of the pole piece 3 or separates therefrom and an output voltage responded to a modulation is obtained in a coil 10 wound on this pole piece 3. At this time, as coil 10 and a coil 9 are wound in opposite directions reverse to each other and are connected in series, and as the pole piece 3 and a pole piece 4 are magnetically connected by a coil holder 6, magnetic fluxes flow in reverse directions the pole piece 3 and the pole piece 4, so that the sum of output voltages of both coils can be taken out. But at this time, the coil 10 and the coil 9 do not have equal output voltages, and almost percent or more of the output voltage is obtained by the coil 10. The reason why the coil 9, which does not provide so much of the output voltage, is necessary, is that is fulfils an important function with respect to the external induction magnetic flux. For instance, the external magnetic flux enters the pole pieces 3 and 4 in the same quantity and in the same direction, so that the same output voltage is generated in the coil 10 and the coil 9, but these coils are wound in the opposite directions and therefore those output voltages cancel each other and the some of these voltages of both coils is zero. There is the advantage that an output does not arise responsive to external induction the voltages.

Vibrator 12 moves perpendicularly to the surface of pole piece 3, and thus moves parallel to the surface of pole piece I at a constant distance from the latter, so that a variation of magnetic flux does not arise in pole piece 1 which does not generate an output voltage. Cancellation of external magnetism occurs in the same manner as stated. When the needle point traces the groove on the outside, the function and operation are reversed with respect to the function and operation thus described.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. An electromagnetic pickup cartridge comprising, in combination, a needle support mounted for vibration in accordance with sound tracks on a record engaged by a needle mounted in said support; a magnetized armature carried by and extending from said support; two pairs of pole pieces arranged in spaced parallel relation, with each pair of pole pieces including a first pole piece and a second pole piece interconnected by a respective magnetic coil holder; only each first pole piece having a pole face at one end in spaced magnetic relation with said armature, said pole faces extending in perpendicular facing relation to each other; said armature being operatively associated with only said pole faces and terminating short of said second pole pieces; and respective coils embracing each of said pole pieces, the coils on each second pole piece being wound reversely with respect to the coil n the associated first pole piece and connected in series therewith; whereby external magnetic fluxes are cancelled with respect to each channel including a first and second pole piece, so that high fidelity reproduction is provided in all channels of the record only by said first pole pieces and the coils thereon in accordance with vibrations of said support relative to said pole faces.

2. An electromagnetic pickup cartridge, as claimed in claim 1, including a vertical compensation plate of mu-metal positioned adjacent said pole faces and said armature.

3. An electromagnetic pickup cartridge, as claimed in claim 1, in which said pole pieces comprise relatively elongated substantially flat bars; each magnetic coil holder comprising a substantially rectangular base and a pair of arms extending upwardly from an outer edge of said base and each juxtaposed with a respective first and second pole piece, said bases being substantially coplanar with their inner edges in adjacent spaced relation; said pole faces comprising bent ends of said first pole pieces bent inwardly toward each other to define an opened vee having an included angle of and said armature intersecting perpendicularly the triangle defined by said pole faces.

4. An electromagnetic pickup cartridge, as claimed in claim 1, in which said support comprises a first lightweight tubular member of non-ferrous metal supporting the needle, and a second tubular armature of ferrous metal supporting said first member and positioned adjacent said pole faces.

5. An electromagnetic pickup cartridge, as claimed in claim 4, including a permanent magnet in operative relation with said armature to magnetize the latter.

6. An electromagnetic pickup cartridge, as claimed in claim 4, including tension means connected to the inner end of said armature and controlling the fulcrum point thereof.

7. An electromagnetic pickup cartridge, as claimed in claim 4, in which said armature is a permanent magnet.

8. An electromagnetic pickup cartridge, as claimed in claim 1, including a cartridge case mounting said pole pieces and said magnetic coil holders; and a needle case mounting said support; said cartridge case and said needle case being formed with interfitting configurations whereby the two cases may be readily engaged with each other and disengaged from each other. 

1. An electromagnetic pickup cartridge comprising, in combination, a needle support mounted for vibration in accordance with sound tracks on a record engaged by a needle mounted in said support; a magnetized armature carried by and extending from said support; two pairs of pole pieces arranged in spaced parallel relation, with each pair of pole pieces including a first pole piece and a second pole piece interconnected by a respective magnetic coil holder; only each first pole piece having a pole face at one end in spaced magnetic relation with said armature, said pole faces extending in perpendicular facing relation to each other; said armature being operatively associated with only said pole faces and terminating short of said second pole pieces; and respective coils embracing each of said pole pieces, the coils on each second pole piece being wound reversely with respect to the coil on the associated first pole piece and connected in series therewith; whereby external magnetic fLuxes are cancelled with respect to each channel including a first and second pole piece, so that high fidelity reproduction is provided in all channels of the record only by said first pole pieces and the coils thereon in accordance with vibrations of said support relative to said pole faces.
 2. An electromagnetic pickup cartridge, as claimed in claim 1, including a vertical compensation plate of mu-metal positioned adjacent said pole faces and said armature.
 3. An electromagnetic pickup cartridge, as claimed in claim 1, in which said pole pieces comprise relatively elongated substantially flat bars; each magnetic coil holder comprising a substantially rectangular base and a pair of arms extending upwardly from an outer edge of said base and each juxtaposed with a respective first and second pole piece, said bases being substantially coplanar with their inner edges in adjacent spaced relation; said pole faces comprising bent ends of said first pole pieces bent inwardly toward each other to define an opened vee having an included angle of 90* and said armature intersecting perpendicularly the triangle defined by said pole faces.
 4. An electromagnetic pickup cartridge, as claimed in claim 1, in which said support comprises a first lightweight tubular member of non-ferrous metal supporting the needle, and a second tubular armature of ferrous metal supporting said first member and positioned adjacent said pole faces.
 5. An electromagnetic pickup cartridge, as claimed in claim 4, including a permanent magnet in operative relation with said armature to magnetize the latter.
 6. An electromagnetic pickup cartridge, as claimed in claim 4, including tension means connected to the inner end of said armature and controlling the fulcrum point thereof.
 7. An electromagnetic pickup cartridge, as claimed in claim 4, in which said armature is a permanent magnet.
 8. An electromagnetic pickup cartridge, as claimed in claim 1, including a cartridge case mounting said pole pieces and said magnetic coil holders; and a needle case mounting said support; said cartridge case and said needle case being formed with interfitting configurations whereby the two cases may be readily engaged with each other and disengaged from each other. 